The situation with high ranked people using two accounts or playing obviously as a clan is pretty annoying, especially when you don't expect it. I suggest before a game starts, at the phase of player selection (choosing game) that there will be a notification on the player's box, a colored circle in the box of the player's name, colored with the color of the player who they have played before together. Inside the circle there will be the number of times they have played together in the past f.i. if the blue player has played with the green before, on the blue player's box there will be a green circle with the number they have played together before. That way, more experienced players can make a conclusion if this is a trap and if they want to continue to play the game or to be prepared what they have to deal with. That way, clans can meet and play together. Simply.